Fix DMA message size calculation

When performing DMA via VFIO-user commands over the socket, vfu_dma_transfer breaks large requests into chunks according to the client's maximum data transfer size negotiated at connection setup time. This change fixes the calculation of the chunk size for the case where the last chunk is less than the maximum transfer size. Unfortunately, the existing test didn't catch this due to the request size being a multiple of that maximum data transfer size. Adjust the test to make the last chunk size a true remainder. Signed-off-by: Mattias Nissler <[email protected]>
nutanix · Jan 24, 2024 · 70dcf91 · 70dcf91
1 parent 2c6239a
commit 70dcf91
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Showing 2 changed files with 6 additions and 5 deletions.
diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
@@ -2312,13 +2312,14 @@ vfu_dma_transfer(vfu_ctx_t *vfu_ctx, enum vfio_user_command cmd,
         if (cmd == VFIO_USER_DMA_WRITE) {
             memcpy(rbuf + sizeof(*dma_req), data + count, dma_req->count);
 
-            ret = vfu_ctx->tran->send_msg(vfu_ctx, msg_id++, VFIO_USER_DMA_WRITE,
-                                          rbuf, rlen, NULL,
+            ret = vfu_ctx->tran->send_msg(vfu_ctx, msg_id++,
+                                          VFIO_USER_DMA_WRITE, rbuf,
+                                          dma_req->count + sizeof(*dma_req), NULL,
                                           dma_reply, sizeof(*dma_reply));
         } else {
             ret = vfu_ctx->tran->send_msg(vfu_ctx, msg_id++, VFIO_USER_DMA_READ,
-                                          dma_req, sizeof(*dma_req), NULL,
-                                          rbuf, rlen);
+                                          dma_req, sizeof(*dma_req), NULL, rbuf,
+                                          dma_req->count + sizeof(*dma_reply));
         }
 
         if (ret < 0) {

diff --git a/test/py/test_sgl_read_write.py b/test/py/test_sgl_read_write.py
@@ -156,7 +156,7 @@ def test_dma_read_write():
 def test_dma_read_write_large():
     ret, sg = vfu_addr_to_sgl(ctx,
                               dma_addr=MAP_ADDR + 0x1000,
-                              length=2 * PAGE_SIZE,
+                              length=2 * PAGE_SIZE + 42,
                               max_nr_sgs=1,
                               prot=mmap.PROT_READ | mmap.PROT_WRITE)
     assert ret == 1